In short: The steel in a slab needs concrete all around it. A few millimetres short today becomes rust inside the slab years later.
What cover is
Cover is the depth of concrete between the steel and the outside face of the slab. It protects the steel from moisture. Bar chairs hold the steel up so the concrete can flow beneath it, and edge spacers keep it off the formwork.
What we found
On a pre-pour inspection in Aintree, next to Deanside, the reinforcement was short of its required cover in more than one area. The same visit found wide ribs missing their extra bars and cut mesh at the plumbing with no trimmer bars.
Why it matters on clay
Ground moisture reaches the underside and edges of every slab. Steel without enough cover can corrode, and corroding steel expands and cracks the concrete around it.
How it is fixed
Before the pour it is simple: more bar chairs and spacers. After the pour there is no practical fix, which is why the inspection is booked for the day before.
Written by our local inspection team from work carried out in Deanside. Licensed building practitioners, Building & Plumbing Commission registration CDB-U 53425.
